The present invention generally relates to gimbaled thrusters and more particularly to methods and systems for providing attitude and momentum control during gimbaled thruster firing for orbit transfer and stationkeeping maneuvers.
Gimbaled thrusters (including Hall Current Thrusters (HCTs)) are used by spacecraft, such as military communications spacecraft, to perform partial orbit transfer. The HCTs, which are much more fuel-efficient than chemical thrusters, enable as much as 500 kg of additional payload to be delivered to the mission orbit.
When used for orbit transfer, the HCTs are fired continuously for several months while the spacecraft attitude is controlled to track an optimal trajectory vector. The attitude control system maintains alignment of the HCT thrust axis and simultaneously rotates the spacecraft for solar array sun pointing. While the HCT fires, fuel-efficient attitude control is required, so the firing of the chemical thrusters (e.g., REAs) for attitude control is not viable. Furthermore, the HCTs are typically mounted on gimbaled platform so that their orientations may be actively modulated to generate control torques. The drawback of using the gimbaled HCTs directly for attitude control is that the resulting gimbal steps (e.g., >10×106) may exceed the life capability of the mechanisms.
Hence, it would be desirable to provide a system that is able to provide more efficient attitude and momentum control during HCT firings for orbit transfer and stationkeeping maneuvers.